• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.190-197
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• 2014

In this paper, we present a method for optical parameter-based material rendering with measuring the thickness of a material using ultrasonic waves. Thickness is an important element in determining the reflectance and transmittance of a material along with its optical characteristics and plays a crucial role in more realistic object rendering. In studies conducted thus far, thickness has been measured and used for rendering. The proposed method is a novel method attempted for the first time ever to render a material considering the thickness of a material whose thickness cannot be measured by visual assessment, using ultrasonic waves. It was implemented by measuring the sound velocity of the reference sample and applying the results to the thickness measurement of other objects that have the same characteristics. The characteristics of the objects measured are reflected in the quality of the final rendering, thus verifying the importance of thickness in rendering.

• Wind and Structures
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• v.12 no.6
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• pp.553-574
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• 2009

This paper presents statistical analysis results of wind speed and atmospheric turbulence data measured from more than 30 anemometers installed at 15 different height levels on 325 m high Beijing Meteorological Tower and is primarily intended to provide useful information on boundary layer wind characteristics for wind-resistant design of tall buildings and high-rise structures. Profiles of mean wind speed are presented based on the field measurements and are compared with empirical models' predictions. Relevant parameters of atmospheric boundary layer at urban terrain are determined from the measured wind speed profiles. Furthermore, wind velocity data in longitudinal, lateral and vertical directions, which were recorded from an ultrasonic anemometer during windstorms, are analyzed and discussed. Atmospheric turbulence information such as turbulence intensity, gust factor, turbulence integral length scale and power spectral densities of the three-dimensional fluctuating wind velocity are presented and used to evaluate the adequacy of existing theoretical and empirical models. The objective of this study is to investigate the profiles of mean wind speed and atmospheric turbulence characteristics over a typical urban area.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.40-47
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• 2000

To obtain the acoustic properties of dispersive polyurethane with high attenuation, through transmission method was applied by ultrasonic. In through transmission method, the sound velocity and attenuation coefficient of specimen were obtained by using Sachse's method which can be applied to small size specimen. But there is a problem when the reference signal is selected, so the result is not precise. The more precise acoustic properties of polyurethane was obtained when two specimens with different thickness were used. To predict the acoustic properties of low frequency range, the acoustic properties extended to the low frequency range were calculated by Kramers - Kronig relation. As a result, we studied on the relation between the sound velocity and the attenuation coefficient with frequency.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.47-54
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• 2003

In this study, the residual stress and the acoustic emission Charactreistics from fatigue crack propagation were investigated, bused on the welded material of STS316L. The residual stress of welding locations could be evaluated by ultrasonic parameters, such as L$_{CR}$ wave velocity and L$_{CR}$ wave frequency； the residual stress between base metal and weld metal was evaluated. In the fatigue tests, three types of signals were observed, regardless of specimen condition, base metal, and weld metal. Based on NDE analysis of AE signals by the time-frequency analysis method, it should also be possible to evaluate, in real-time, the crack propagation and final fracture process, resulting from various damages and defects in welded structural members.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1243-1246
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• 1987

To characterize the biological tissues, the new methods to measure the frequency dependent attenuation are presented in this paper. In general, ultrasonic phase information was assumed by linear function of the frequency. But, the minimum phase function which characterizes the frequency dispersion of tissue was derived in [l]. It is very significant to measure the attenuation by using the minimum phase function to characterize the frequency dispersion of tissue. Therefore, a more efficient method measuring the frequency dependent attenuation are proposed by using the estimated sound velocity and polarity of reflected signal. To verify the algorithms, pulse reflection experiments are performed.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.133-137
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• 2012

Cracking may be used to help predict the cause of deterioration of concrete, since in many cases characteristic cracking patterns are produced. The purpose of this paper is an analysis of the crack cause occurred in concrete faced rockfill dams. We analyzed the concrete placement methods, cracking pattern, the inspection of crack depth by the ultrasonic pulse velocity method, and the measurement of heat of hydration, environmental condition, and so on. In this study, the crack cause of concrete faced rockfill dam is the wrong method of concrete placement, high temperature difference by cement of heat of hydration and concrete of drying shrinkage.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.11 no.1
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• pp.33-38
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• 2008

To investigate the building wind characteristics of skyscraper nearby areas, two points were selected and the wind speed and the wind direction data were measured using 2-D ultrasonic anemometer and propeller type wind monitor during the winter time. The study site is Dohgok-dong, Seoul. After measurement, wind data whose speed is equal to or more than Beaufort level five were selected, classified and analyzed in terms of direction, velocity level and hourly difference. The prevailing wind point is higher than street canyon in terms of intensity and frequency. The main direction is also different. This study aims to figure out the phenomena of building wind impact and also to provide essential basic data for establishing proper guidelines in building wind impact assessment for skyscrapers in Korea.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.155-162
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• 2023

In nuclear power plants, the flow rate information is a major indicator of the performance of rotating equipment such as pumps, and is a very important one required for facility operation and maintenance. To measure a flow rate, various types of methods have been developed and used. Among them, the differential pressure type using orifice and the direct doppler type using ultrasonic waves are the most commonly used. However, these flow rate measurement methods have limitations in installation, conditions and status of the measuring part, etc. To solve this problem, we have studied a new technique for measuring flow rate from scratch. In this paper, we have devised a technique to estimate the flow rate using an average moving velocity of large-scale eddy in turbulence that occurs in the piping flow field. The velocity of the large-scale eddy can be measured using the pressure fluctuation signals on the inner surface of the pipe. To estimate the flow rate, at first a cross-correlation function is applied to the two pressure fluctuation signals located at different positions in the down stream for calculating the time delay between the moving eddies. In order to validate the proposed flow rate estimation method, CFD analyses for the internal turbulence flow in pipe are conducted with a fixed flow condition, where the pressure fluctuation signals on the pipe inner surface are simulated. And then the average flow velocity of the large scale eddy is to be estimated. The estimated flow velocity is turned out to be similar to the fixed (known) flow rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4B
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• pp.357-363
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• 2009

When yields the mean velocity of the closed conduit which is used generally, it is available to use Darcy Weisbach Friction Loss Head equation. But, it is inconvenient very because Friction Loss coefficient f is the function of Reynolds Number and Relative roughness (${\varepsilon}$/d). So, it is demanded more convenient equation to estimate. In order to prove the reliability and an accuracy of Chiu's velocity equation from the research which sees hereupon, proved agreement very well about measured velocity measurement data by using Laser velocimeter which is a non-insertion velocity measuring equipment from the closed conduit (Laser Doppler Velocimeter: LDV) and an insertion velocity measuring equipment and the Pitot tube which is a supersonic flow meter (Transit-Time Flowmeters). By proving theoretical linear-relation between maximum velocity and mean velocity in laboratory flume without increase and decrease of discharge, the equilibrium state of velocity in the closed conduit which reachs to equilibrium state corresponding to entropy parameter M value has a trend maintaining consistently this state. If entropy M value which is representing one section is determinated, mean velocity can be gotten only by measuring the velocity in the point appearing the maximum velocity. So, it has been proved to estimate simply discharge and it indicates that this method can be a theoretical way, which is the most important in the future, when designing, managing and operating the closed conduit.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1070-1077
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• 2011

This study intends to assess the defect in the weld zone of titanium grade 2 plate in terms of acoustical anisotropy based on the angle beam method. Depending on the rolling direction, the ratio of wave velocity was found to be 1.08 and the difference in the angle of refraction was more than seven degrees, confirming the presence of acoustical anisotropy. Thus for measuring the length of defect in the weld zone of the titanium plate (thickness of 10mm), the distance amplitude characteristics curves of titanium, TDACC-R and TDACC-T were constructed for the measurements in consideration of the acoustical anisotropy on CRT of the ultrasonic testing equipment. As a result, when the distance amplitude characteristics curve corresponds to the rolling direction, the length of defect was close to the actual measurement within 1mm and when different, the difference was found to be over 4mm. It was affirmed that the acoustical anisotropy should be taken into consideration when measuring the length of defects in the weld zone of the titanium plate with the presence of acoustical anisotropy.